Currently, liquid crystal display with TFT-LCD as a representative has been an important flat panel display manner. In view of the directions of the electric fields driving the liquid crystal, the TFT-LCD is divided into a vertical electric field type and a horizontal electric field type. The vertical electric field type TFT-LCD comprises a Twist Nematic (TN) type TFT-LCD; the horizontal electric field type TFT-LCD comprises an FFS type TFT-LCD and an In-Plane Switching (IPS) type TFT-LCD.
During the manufacturing of the TFT-LCD array substrate, a protection layer 7 is coated after a data line is formed, as illustrated in FIG. 1. The protection layer 7 covers the whole of the display area (that is, area d), and a resin through hole needs to be formed not only in a common electrode through hole area (that is, area a), but also in a peripheral Electro Static Discharge (ESD) prevention area (that is, area b) and a chip bonding (IC bonding) area (that is, area c). As resin is a planarization material and presents a planarization shape on the whole after being coated and cured. If the bottom layer structure of the resin has sharp fluctuation, differences of the thickness of the resin will be rendered, as illustrated by the four areas a, b, c and d in FIG. 1.
As the resin needs dry etching, the resin in area b is the thinnest, it can be etched in the shortest period, and areas a and c need a longer etching period. Suppose the etching speed of the resin is x and thicknesses of the areas a, b and c are represented by Ta, Tb and Tc, respectively, the etching period of the three areas can be represented with Ta/x≅Tc/x>Tb /x. When the etching of the area b is finished, the resin in areas a and c is still being etched, thus the bottom layer data line 4 in the area b will be damaged greatly. Suppose the etching speed of the data line is y, the over-etching amount of the data line can be represented with (Ta/x−Tb/x)*y. As the data line per se is thin, over-etching will easily render the defect of data line loss, and then product yield is lowered.